Using the Hubble Space Telescope, astronomers have for the first time mapped the plasma “belch” of a supermassive quasar powered by a black hole relatively close to Earth.
While supermassive black holes with masses of millions or billions of times the mass of the Sun are thought to reside at the heart of all galaxies, not all of these cosmic titans power quasars. Some, like the supermassive black hole at the heart of the Milky Way, called Sagittarius A*, are relatively silent as they voraciously feed on the matter around them.
This particular quasar, and the predatory supermassive black hole that powers it, is located at the active heart of the Zwicky 1 galaxy, about 847 million light-years from Earth in the constellation Pisces. Although this is an incredibly large distance, most quasars exist in the early universe, meaning they can be billions of light years away.
So the proximity of this quasar, called “I Zwicky 1,” makes it an excellent laboratory for studying the extreme conditions around active galactic nuclei (AGN), regions so bright that they can outshine the combined light of every star in the galaxies they surround. them. This includes “burps” or ejections of matter from the surroundings of the supermassive black hole.
The supermassive black hole at the heart of Zwicky 1 is estimated to have a mass equivalent to 9.3 million suns. It is thought to consume matter at an incredible rate, producing powerful jets that propel high-speed “burps”. A team of astronomers from the Netherlands Institute for Space Research (SRON) described these outflows for the first time.
“Even Zwicky 1 is very special in its characteristics,” team leader Anna Juráňová said in a statement. “Other quasars have similar outflows, but in this one everything is just right. Our angle of view, the width of the lines in the spectrum and so on. This allows us to penetrate much deeper into its processes. We have created a global picture of the movements of ionized gas in a quasar, which is rare .”
How quasars acquire their outflows
Like all black holes, supermassive black holes are surrounded by an outer boundary called the event horizon. This is the point at which the black hole’s gravitational influence has become so intense that even light is not fast enough to reach its escape velocity.
Since nothing with mass can travel faster than the speed of light, it might lead you to wonder how these outflows escape quasars. The answer is that the material that contains the outflows never crosses the event horizon.
When a supermassive black hole is surrounded by matter, whether gas and dust or the remains of a star that the black hole has crushed with its immense gravity, that matter has angular momentum. This means that it cannot fall directly into a black hole and instead forms a rotating flat cloud around the black hole called an “accretion disk”.
Matter in the accretion disk is gradually fed into the central supermassive black hole, but if there’s one thing scientists know about black holes, it’s that they’re messy eaters. Not all matter in accretion disks is destined to fall into a black hole; some charged particles are directed to its poles by strong magnetic fields.
These magnetic fields accelerate the trapped particles to speeds that are a significant fraction of the speed of light, and are then fired as highly collimated jets. These jets and their associated radiation expel clouds of matter from around the supermassive black hole, and these are the outflows the team mapped for I Zwicky 1.
Using HST, Juráňová and colleagues discovered the properties of four different plasma outflows from around I Zwicky 1. They found that they were moving at speeds between 134,000 mph (217,000 km/h), 200 times the speed of sound, and a staggering 6.5 million mph. (10.5 million km/h), which is about 8,500 times the speed of sound and about 1% of the speed of light.
The team also found that one of the outflows appears to be “caught in the shadow” of another black hole outflow. This occurs when radiation from the accretion disk, in the form of ultraviolet light, is absorbed by elements such as nitrogen, oxygen and carbon in the clouds of matter near the black hole and pushed away as a result.
Not only is this the first time astronomers have seen this mechanism at play, but it reveals to researchers that the immediate vicinity of I Zwicky 1 is more active than the AGN homes of other quasars.
“Our data indicate that far more gas is rising and blowing out of the disk around the black hole,” concluded Juráňová. “This insight brings us closer to unraveling the way these supermassive black holes grow and interact with their surroundings.”
The team’s research was published online Tuesday (June 11) in the journal Astronomy & Astrophysics.